Liquid dispensing systems are used in a variety of industrial applications. For example, in the case of hot melt adhesive dispensing systems, heated liquid adhesive is conveyed through an elongated heated hose from a melter unit having a hot melt supply tank, heated manifold and pump to a remote hot melt dispensing gun. The dispensing gun receives molten hot melt adhesive from the melter unit through the heated hose. In some applications, multiple dispensing guns are connected to a single melter unit through a set of hoses with each hose being connected to a different dispensing gun.
Each dispensing gun and hose, as well as parts of the melter unit, includes a separate heater which must be operated within a predetermined temperature range to provide the proper viscosity for the particular hot melt adhesive used in the dispensing application. To monitor the temperature of the hot melt adhesive throughout the dispensing system, each component includes a temperature sensor which is electrically coupled to a controller of the system. The controller senses the temperature within each component through the respective temperature sensors and operates the heaters within the melter unit, hose and dispensing gun to maintain the hot melt adhesive within the predetermined temperature range.
Dispensing guns in operation, such as those used in packaging or diaper manufacturing lines, are typically located remote from the melter unit. For example, one dispensing gun may be located relatively close to the melter unit (i.e., four (4) feet, for example) while other guns maybe located at various distances from the melter unit (i.e., eight (8), ten (10) and twelve (12) feet, for example). The distance of the guns from the melter unit can cause significant problems when the line is being setup or during diagnostics and maintenance of the dispensing system by an operator. In particular, hoses are traditionally monochrome in color, with a vast majority of them being completely black. When a line is being setup, it is often difficult and time consuming for an operator to select the correct length of hose for each gun to ensure that each hose will have a sufficient length, without excessive slack, to reach its associated gun from the melter unit. The same problem occurs during maintenance and diagnostics when the ends of the hoses are disconnected from either the melter unit, the guns, or both. The operator must then determine which hoses are to be connected to the various guns of the system which can cause the system to operate improperly if the hoses are not reconnected in their proper positions.
In addition, care must be taken when selecting and connecting hoses between the melter unit and the guns since the temperature sensing devices within the hose and gun must be compatible with the controller of the system. For example, one particular temperature sensing device commonly used in the melter unit, hoses and guns is a resistance temperature detector (RTD) which may be made from different materials, such as nickel or platinum. A nickel RTD must be connected to a controller compatible with a nickel RTD, while a platinum RTD will only work properly with a controller compatible with a platinum RTD. If the RTD type of the hose and gun is not properly matched to the appropriate, material-specific controller, the controller may provide erroneous temperature information about the hot melt adhesive in the hose and gun and may cause the heating devices within these components to operate improperly.
A still further complication in proper setup and maintenance of the dispensing system is caused by the need for proper selection of a solenoid to control operation of solenoid-operated dispensing guns. For example, with pneumatic guns operated by a pressurized air controlled through operation of a solenoid, such as the pneumatic dispensing gun fully disclosed in U.S. Pat. Nos. 4,066,188, 5,277,344 and 5,934,520, owned by the present assignee and the disclosures of which are hereby incorporated herein by reference in their entirety, the solenoid is connected to a source of pressurized air to control actuation of a pneumatically-controlled valve within the gun. Each solenoid has a particular air volume capacity rating, voltage requirement and/or temperature rating which must be properly selected by the operator to meet the specific application needs. Improper selection of the solenoid may result in failure of the dispensing gun to provide the desired pattern of hot melt adhesive on the substrate. This can lead to significant downtime of the dispensing line.
For reasons such as those described above, it would be desirable to provide components of a liquid dispensing system that assist an operator in the proper selection of the components and in the configuration of those components in the system during setup, maintenance and diagnostics. It would also be desirable to assist an operator in the proper selection of a solenoid for use in a particular liquid dispensing application.